Interpolymers of caprolactam, hexamethylene diamine, adipic acid and sebacic acid



y 30, 1967 D. B. cooK ETAL 3,

INTERPOLYMERS OF CAPROLACTAM, HEXAMETHYLENE DIAMINE, ADIPIC ACID AND SEBACIC ACID Filed April 23, 1963 WEIGHT cm wo c 40p The present application is a continuation-in-part of United States Ser. No. 196,744, filed May 22, 1962, and now abandoned.

This invention relates generally to the melt-spinning of synthetic polymeric filaments and, more particularly, to the production of nylon filaments especially adapted for use in hosiery.

It is well known that nylon has almost completely replaced silk and other fibers in the womens hosiery field. Although commercially available nylon hosiery yarn is entirely suitable in most respects, there is a need for improvement, especially in connection with such factors as fit and comfort. This need arises from the fact that the standard sizes of hose which are available do not pro vide a satisfactory fit for all wearers. In many cases, the hose which provides a good fit for one part of the leg does not provide an adequate fit in other places, e.g., if the hose fits properly at the ankle, the knee will be too tight. These factors have led to the production of stretch hose which provide improvements in fit and comfort due to their capability of adapting to the larger parts of the leg. However, the greater portion of todays market is still held by nylon hose of standard construction and there is a continuing need for improvements in such factors as hose fit, comfort, aesthetics and durability, as well as in yarn processability.

The general objective of the present invention is to provide improved polyamide filaments for the production of hosiery. A more specific objective is to provide uncrimped polyamide filaments which when processed into non-stretch hosiery provide better fit and comfort than can be obtained with commercially available synthetic filaments. Another object is to provide hose having superior aesthetic qualities or, alternatively to provide hose of improved durability at equivalent aesthetic levels.

These and other objectives are accomplished with a filament prepared from the copolymer reaction product of hexamethylene diammonium adipate and caprolactam or from the terpolyrner reaction product of hexamethylene diammonium adipate, hexarnethylene diammonium sebacate, and caprolactam. Weight percentages of the above reactants may be varied within limits, as long as they fall in the area ABCDE shown in the appended drawing. The filaments are further characterized by a Nuclear Magnetic Resonance (NMR) loosening factor of greater than 1.0 and an initial modulus no greater than 12 grams/ denier, as determined on filaments after boiling in water at 90l00 C. for 15 minutes.

It has been found that in order to obtain hosiery of improved fit characteristics, the shrinkage tension of the yarn must be lower for a given shrinkage level than that found in prior art yarns, i.e., the ratio of shrinkage-tension/shrinkage must be low. In addition, the yarn must have a low initial modulus and the shrinkage potential must be relatively high for use in hosiery leg yarn. These characteristics are achieved by processing filaments of the composition defined above under carefully selected conditions.

Filaments are prepared by melt extrusion of a copolymer or terpolymer fiake of the above-described composition, followed by quenching and cold-drawing to produce highly-oriented structures. The drawn filaments are heat- 3322,73 l Patented May 30, 1967 ed under conditions of controlled relaxation, at a temperature and for a time sufficient to achieve an NMR loosening factor greater than 1.0 and a shrinkage-tension/ shrinkage ratio of less than 0.70.

When a drawn filament of the prescribed composition has an NMR loosening factor of greater than 1.0, preferably at least 1.2, the desired shrinkage-tension/shrinkage ratio is achieved. Nuclear magnetic resonance measurements indicate motional constraint of molecular segments in the filaments, the degree being shown by the width of a broad absorption band. This motional constraint has been labeled matrix rigidity. Since the shrinkage tension and shrinkage measurements are obtained in a hot 100 C.) water treatment, the matrix rigidity is measured in water at room temperature and at the boil. It is the difference in these measurements which is referred to herein as the loosening factor.

Matrix rigidity is measured using the nuclear magnetic resonance equipment of Varian Associates, model V-4302 dual purpose spectrometer, and using their high temperature probe insert Model No. V-433l-TWL and using 56.4 mc./s. radio frequency energy. Yarns are wrapped taut around very thin glass rods and the ends tied to prevent shrinkage during the heating experiment. This wrapping provides a random placement of the fiber axis with respect to the magnetic field direction so that an average NMR spectrum is obtained at any temperature. As described in J. G. Powles, Polymer, 1, 219-265 (1960), polymers give a broad absorption spectrum which can be characterized by halfwidth (peak-to-peak distance of the derivative output curve, expressed in gauss) herein called matrix rigidity. Values are obtained, using 17 db attenuation of the RF field and with a sweep modulation of 1 gauss. To obtain values of the loosening factor, the vacuum dried yarns are soaked overnight in D 0 while wrapped taut and then are heated while immersed in excess D 0. D 0 is used to prevent an NMR signal from the protons in H O. Data points are obtained about every 5 C. while heating the yarn in the NMR instrument during an approximate two-hour period. The matrix rigidity value at 100 C. is obtained as an extrapolation of the straight line through the data points between room temperature and about -98 C. This value at C. is subtracted from the matrix rigidity value of the soaked yarn at room temperature to obtain the loosening factor.

Where reported herein, filament shrinkage is determined by measuring a length of the filament when held under sufiicient tension to keep it straight without stretching, subjecting the measured length to boiling water in a relaxed state for fifteen minutes, drying and measuring the boiled-off length. The percent shrinkage is then calculated from the two measurements.

Shrinkage tension is determined by removing a length of yarn from the package, permitting it to relax for 24 hours, placing a sample of the yarn between the jaws of a commercial Instron tester, the jaws being spaced 10 inches part, immersing the yarn sample in 90 C. Water for five minutes, withdrawing the then tensioned sample and permitting it to cool and dry at room temperature for five minutes. The tension in grams is then read from the Instron chart and converted to grams/ denier, the denier of the yarn before the test being determined by weighing a known length on a suitable balance.

The relaxed sample used in the shrinkage tension determination is conditioned at 74 F. and 72% r.h. before placement between the spaced Instron jaws and the test is carried out under these conditions. The water bath used for immersion of the yarn is contained in a cylindrical vessel of about 6" diameter and 16" length. The vessel is situated just below the lower clamp of the tester and is moved vertically upward to immerse the sample. Hot water is circulated through the container, which is insulated, to maintain a temperature of 90:1 C. After the 5-minute immersion period the Water bath is moved downwardly to its original position. The top of the Water container is sealed with a rubber gasket to prevent water vapor from the hot Water escaping into the atmosphere around the sample While the sample is being intially positioned or While it is drying after immersion.

The shrinkage-tension/ shrinkage ratio mentioned above is calculated by dividing the shrinkage tension, measured in grams per denier, by the percent shrinkage in boiling water and multiplying the resulting quotient by 100.

Initial modulus is indicative of the rate at which yarn. elongates With increasing load in the early stages of elongation. Practically, it is determined from the stress-strain curve (obtained when the boiled off yarn is elongated 2% in an Instron tester) by multiplying the load at 1% elongation by 100 and dividing by the denier of the yarn.

Example I After charging 60.3 lbs. of a 48.8% aqueous solution of hexa-methylene diammonium adipate (66 nylon salt solution), 1.9 lbs. of 35.1% aqueous solution of hexamethylene diammonium sebacate (6-10 nylon salt solution) and 3.9 lbs. of caprolactam (i.e., 4.5 lbs. of e-EiIIllIlO caproic acid to which it hydrolyzes) to an evaporator, 9.3 lbs. of water are removed by evaporative heating at atmospheric pressure. The charge is then transferred to an autoclave, heated to a temperature of about 210 C. and brought to a pressure of 250 p.s.i. At this point, 205 grams of a aqueous slurry of titanium dioxide are added. The solution is then heated at 250 p.s.i. until the temperature reaches 274 C. When the temperature reaches 230 C., 0.48 gram of Mn(H PO in 200 m1. of Water is added. After the heating period, pressure is reduced over a period of 90 minutes to atmospheric and temperature is increased to 279 C. The polymer is then held for 60 minutes at this temperature after which it is extruded under 50-70 p.s.i. nitrogen in the form of a ribbon which is quenched on a watercooled casting wheel and cut into %-1I1Ch flake in the conventional manner. The polymer flake contains 85% of 6-6 units, 2% of 6-10 units and 13% of 6 units and has a relative viscosity of 55.

Proceeding as above, except that the concentrations of starting materials are varied, copolymers and terpolymers having the compositions given in the following table are prepared. Plot points for the several compositions from which the illustrated operable area ABCDE Was determined have been indicated parenthetically in Table 1.

The various batche of polymer are melted on a grid, extruded, air quenched and wound into packages at 361 yards/minute in the conventional manner. The filaments are then cold drawn over a pin at a ratio of 4.74 and wound into a filling wound drawtwister package (15- denier monofilaments having a 0.5 Z-twist).

The cold drawn filaments prepared from most of the tabulated compositions, after standing for 24 hours, are given a hot annealing and relaxation treatment to lower the shrinkage level. This is accomplished by several passes of the filaments over a 3-inch steam-heated hot plate placed between two stepped rollers, the rollers having sufficient variation in diameter to permit .a retraction in length of 2.5%. The hot plate temperature is varied from 150 to 200 C. depending upon the severity of heat treatment required to reduce boil-off shrinkage into the desired range of 12-15%. The filaments contact the hot plate at a speed of 205 y.p.m.

Shrinkage tensions, initial moduli and tenacities are measured on relaxed filaments from the above compositions, the modulus and tenacity measurements being made after boiling in water in a relaxed state and drying. For comparison, similar tests are made on filaments from 6 and 6-6 nylon. Results of these tests are reported in Table 1. Values for shrinkage, shrinkage-tension/shrinkage factor (m) and NMR loosening factor are also given. The compositions listed in Table 1 are based upon starting materials, i.e., hexamethylene diammonium adipate, hexamethylene diammonium sebacate and e-amino caproic acid (to which caprolactam hydrolyzes).

The IS-denier filaments are knitted into hose in the conventional manner on a single-feed Scott and Williams seamless knitting machine (400 needles) to yield preboarded course counts of about c.p.i. (courses/inch) in the knee when measured on the table top. Forty denier, 13-filament yarn of the same polymer composition is used for the welt, heel and toe regions of these hose which are preboarded using a board having a width of 6 inches at the knee, 4% inches at the calf and 2% inches at the ankle. The hose, pulled down loosely on the board, are exposed to 6 p.s.i. steam for three minutes.

A number of hose prepared as described above are dyed according to standard conditions except for a lower dye bath temperature (150 F.) and then post-boarded at 180 F. for one minute. The hose were subjected to wear tests in which they were worn by women having small, average and large legs. Each wearer rated the hose on fit, wrinkling and bagging in the ankle, calf, and knee. For comparison, hose knitted from commercial 6 and 6-6 nylon yarns were tested and rated in a similar fashion. Many wearers having average size legs noticed an improvement in fit and comfort over hose from commercial yarns. Those wearers with small legs found a very substantial improvement in fit and comfort when wearing the hose of this invention as compared to the commercial hose. Likewise, those wearers with large legs found the hose of this invention to be more comfortable and improved in fitting properties compared to hose from commercial yarn.

Compost Initial Tenacity, Shrinkage, Shrinkage NM R Intcrpolymcr tion, Modulus, g.p.d. percent Tension, m Factor percent g.p.d. g.p.d.

66/610/6. 85:10:5 12.0 4. 6 12 0.065 0. 54 1. i) 66/610/6- :10:10 6. 6 4. 2 14 0. 083 0. 59 66/610/6 (E) 77:10:13 6.3 4.1 13 0. 074 0. 57 66/610/6 (D) 75:20:51 8.3 4.1 12 0.073 0. 61 66/610/ 70:20:10 7. 3 2. 2 13 0.112 0. 8G 66/610/6 (C) 9:5: 8. 2 4.1 13 0v 088 0. 68 66/6 :15 7. 5 4. 6 14 0.067 0. 48 66/6. 83:17 6. 7 4. 7 14 0. 081 0. 58 (is/(L 87:13 8. 3 4. 3 12 (l. 080 0.67 66/6 (A) so: 20 5. a 4. 3 13 0. 082 0. as /6 75:25 5.2 3.3 14.7 0.136 092 66/6 (B 90:10 7. 7 4. 4 13 0. 082 0. 63 66/610 85:15 11 4. 5 12 0.139 1. 16 66 Control. 16 6.3 10 0.136 1. 36 6 Control 100 9 4. 6 14 0. 0. 93

Copolymer fiage containing 85% 6 6 and 15% 6 poly mer units is prepared as described in Example I. The polymer flake is coated with dry calcium terephthalate by the overlying filaments. Such microcrimp reduces the yarn coefiicient of friction relative to that in the inner and outer layers. The elfect is .a variation in length of successive hose knitted from the same yarn package.

at of 5 ITllCI'OIlS in diameter, by rotating the flake with the powlen th is substantian reduced der in a drum-type dr-yer at room temperature. Sufficient i hose from 3 F and J are p p and terephthalat? powder 18 mated i the flake to wear-tested as described in Ex ample I substantial improvlde a .eeneentratlen 9 2% by Welght m polymer provements in comfort and fit are obsefved in compariafter meltlng and extrusion. The coated flake is melted, 10 son with hose from arms Handl extruded, and cold-drawn to form ZO-denier monoy filaments as described in Example I. The draw ratio for Example III yarns F and G (Table 2) is 4.88, while that for yarns A copolymer Containing 85% 66 and 6 polymfir and J 18 15 units is prepared, extruded and cold drawn at a ratio The yams are stlblected to 21,1101 anneahngfind relaxa' of 4.75 as described in Example H, except that the caltreengent' g 1S aeeempclllshed by g fi eg cium terephthalate is omitted. From the drawing step the m a er 0 Passes areun a Steppe. r0 er an yarn is passed continuously through an annealing and reassoc1ated separator roller, the yarn passmg over a 3-1nch laxafion Step of the type described in Example 11, except P plateelmated between the two r The e plate 20 that the heating element between the rollers provides 4 mallnamed at 180 the yarn 15 passed m of contact with the yarn on either side or a total contact Wlth the plate at a Speed of 205 The Y 18 of 8" for each complete pass of the yarn around the gwen two peeeee around the larger dlameter porno? Of rollers. The temperature of the heating element is shown the rollers and two passes around the smaller portions, in Table 3 Yams K and L are given 5 passes around the the percentage relaxanen. aehleved m gemg. from the larger portions of the rollers for constant length anneal- $552; 2. 3: g g g 323?; g i e g Table ing and 5 passes around the smaller portions to provide 0 5 hour ective] pbetween g i a 5 t 13% retraction in length. Yarn M is given 10 passes treatment Whige H I and J a ng ea around the larger portions of the rollers and the relaxatinuousl with: n z r e eg i tion step is omitted. The yarn is passed in contact with dully h k a i k i g i g 1a the heating element at a speed of 788 y.p.m. Values obe j s S enslon an tained on these yarns for tenacity, initial modulus, shrinkenmg aetor Va ues ,etermmed for each of thejyams age, shrinkage tension, the shrinkage-tension/shrinkage the reams m Table Also shown 15 the factor and NMR loosening factor are shown in Table 3. shnflkage'ienslon/Shnnkage factor ml It 13 'flpparent For comparison, values obtained on a cold-drawn yarn on p of tabulatfid results that satlsfactofy N without heat treatment are shown. When hose from VEllllS for the loosening factor and the shrinkageyarns K and L are prepared as dgscribgd Example I, t lsi n s i kage f r r Obtained ,2- relaXatiOIl substantial improvements in comfort and fit are observed when the yarn is allowed to stand for 30 minutes or more as compared to hose from yarn M.

TABLE 2 Standing Relaxa- Initial Tenacity, Shrinkage, Shrinkage 'NMR Yarn Tune tron, Modulus, g.p.d. percent Tension m Factor percent g.p.d.

TABLE 3 Relaxa- Temp., Initial Tenacity, Shrinkage, Shrinkage NMR Yarn tion, C. Modulus, g.p.d. percent Tension 1n Factor percent g.p.d.

K 13 100 5. 0 4.0 17. 7 0. 084 0. 47 1. 5 L 13 200 0. 0 5. 2 12. 0 0. 071 0. 50 1. 5 M None 220 7. 0 5. 3 12. 0 0. 100 0.82 0. 9 N 5. 3 3. s 22. 3 0. 119 0. 53 0. 7

between cold drawing and heat treatment. However, when this standing time is eliminated, a relaxation of around 13% is required to obtain the desired result.

The coefficient of friction of the filaments containing calcium terephthalate is found to be about 0.51, as compared to a value of about 0.85 for similar filaments containing no calcium terephthalate. The lower value indicates a modification of the surface to produce a filament which develops less friction and consequently less tension in passing through yarn guides in textile machinery.' This is confirmed when it is found that tension on the filaments during knitting is much more constant than is usually the case. Normally the tension varies appreciable due to the fact that the yarn in the middle of a package has a microcrimp as a result of having been compressed Hose prepared from the filaments of tihs invention are observed to have a softer and more pleasing hand than 6-6 nylon hose prepared from the same denier yarn. Thus, the exemplified 20 denier filaments produce hose which are equivalent in hand and superior in durability to 15 denier 6-6 nylon hose.

The described functional improvements have been attributed to the fact that hose knitted from filaments prepared according to the teachings of our invention exhibit a much rounder and more evenly spaced stitch than is observed in hose prepared from prior art filaments. The round stitch contributes to considerably greater transverse stretchability with the result that hose which are small enough to fit snugly in the ankle will give sufficiently to provide a good and comfortable fit in the calf tension/shrinkage factor be low, i.e., less than about 0.7.

Filaments with higher factors tend to shrink down so strongly when the hose are boarded that the stitches be- .come square and the transverse stretchability is decreased.

To achieve the desirably low shrinkage-tension/ shrinkage factor, the NMR loosening factor must be greater than 1.0 and preferably at least 1.2. It is also necessary that the filaments have a low initial modulus. The desired structure is obtained by selection of a polymer compositron from those copolymers and terpolymers defined by the area ABCDE in the drawing and by processing of filaments from this composition under carefully selected conditions. While it will be noted that cold-drawn fila ments from the polymer composition of this invention sometimes yield a low shrinkage-tension/ shrinkage factor, such filaments have a much lower tenacity than the heattreated filaments and the shrinkage is undesirably high. Such filaments do not exhibit the desired NMR loosening factor.

In order to achieve the desired structure, the colddrawn filaments must be allowed to stand for at least about 30 minutes and then subjected to a hot annealing and relaxation treatment, the relaxation being of the order of 2-3%. Alternatively, the cold drawing and heat treatment may be carried out continuously, in which case a relaxation of about 12-15% is required to achieve the desired structure. As is apparent from Table 1, polymer systems outside the area ABCDE do not give the desired shrinkage-tension/ shrinkage factor and, in some instances, the filament tenacity is too low. Tenacities below about 4.0 g.p.d. after boil-off are undesirable for producing hosiery of satisfactory durability. For practical reasons, the preferred polymers are the copolymers of 6-6 and 6 nylon which fall within the prescribed area.

The shrinkage of the filament in boiling water should fall in the range of about 845%, in order that hose of the desired fit and comfort be attained. With lower shrinkages, hose cannot be shrunk down to fit a board having the necessary dimensions to achieve satisfactory fit for wearers having legs of smaller than average size. Welt yams will, of course, have a lower shrinkage.

The low initial modulus of the filaments of this invention contributes a great deal to improvements in fit and comfort and is also important inproducing a hose with a softer hand. It is thus possible to produce a more durable hose by increasing the filament denier Without suffering any disadvantage in aesthetics. For instance, 20 denier monofilaments of the present invention may be substituted for 15 denier monofilaments of 6-6 nylon with no loss in aesthetic properties. In order to achieve the desired level of aesthetics, the initial modulus after heating in 90100C. water should be no higher than 12 g.p-.d.

Filament properties are further enhanced by the incorporation therein of a finely divided salt of terephthalic acid as a surface modifying agent. For this purpose, the salt should be dispersed in amounts ranging from 0.l%, preferably 0.253%, by weight of the interpolymer. The preferred salt is calcium terephthalate.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. An oriented filament consisting essentially of an interpolymer composition selected from the group consisting of:

(1) the copolymer of from to of e-amino caproic acid and from 80% to 90% of hexamethylene diammonium adipate, and

(2) the terpolymer of from 5% to 20% of e-amino caproic acid, up to 20% of hexamethylene diammonium sebacate and from 75% to 90% of hexamethylene diammonium adipate, all percentages expressed being by weight, the said filament being characterized by a shrinkage tension to shrinkage ratio of less than 0.7 and a boil-off shrinkage of 815%, wherein the shrinkage tension is determined by immersing a given length of yarn into water at a temperature of 90 C.il C. for about five minutes, restraining the yarn to prevent shrinkage, withdrawdrawing the sample and allowing it to dry at room temperature for about five minutes, and measuring the yarn tension in grams/ denier.

2. The filament of claim 1 further characterized by an initial modulus no greater than 12 grams/denier and a tenacity of at least 4 grams/ denier, said initial modulus and said tenacity being determined after relaxed state boil-01f of said filament.

3. The filament of claim 1 further characterized by an nuclear magnetic resonance loosening factor greater than 1 and an initial modulus no greater than 12 grams/ denier, said initial modulus being determined after relaxed state boil-off of said filament.

4. The filament of claim 1 wherein said interpolymer composition is a substantially 85:15 co olymer of hexamethylene diammonium adipate and e-amino caproic acid, respectively, all percentages expressed being by weight.

5. The filament of claim 1 wherein said interpolymer composition is a substantially 85:2: 13 terpolymer of hexamethylene diammonium adipate, hexamethylene diammonium sebacate and eamino caproic acid, respectively, all percentages expressed being by weight.

6. An oriented nylon filament consisting essentially of an interpolymer composition selected from the group consisting of (l) the copolymer of from 10% to 20% of e-amino caproic acid and from 80% to 90% of hexamethylene diammonium adipate, and

(2) the terpolymer of from 5% to 20% of e-amino caproic acid, up to 20% of hexamethylene diammonium sebacate and from to 90% of hexamethylene diammonium adipate, all percentages expressed being by weight, the said filament being characterized by an nuclear magnetic resonance loosening factor greater than 1 and an initial modulus no greater than 12 grams/denier, said initial modulus being determined after relaxed state boil-off of said filament.

7. An oriented nylon filament useful in the knitting of hosiery consisting essentially of the copolymer of from 10% to 20% of e-amino caproic acid and from to hexamethylene diammonium adipate, all percentages expressed being by weight, the said filament characterized by a shrinkage tension to shrinking ratio of less than 0.7, a boil-off shrinkage of 8-15%, an initial modulus no greater than 12 grams/denier and a tenacity of at least 4 grams/denier, wherein the shrinkage tension is deter mined by immersing a given length of yarn into water at a temperature of 90 Oil C. for about five minutes, restraining the yarn to prevent shrinkage, withdrawing the sample and allowing it to dry at room temperature for about five minutes, and measuring the yarn tension in grams/denier, said initial modulus and said tenacity being determined after relaxed state boil-off of said filament.

8. The filament of claim 7 further characterized by an nuclear magnetic resonance loosening factor of at least 1.2.

9. An oriented nylon filament useful in the knitting of hosiery consisting essentially of the terpolymer of from 2% to 20% or hexamethylene diammonium sebacate, from 5% to 20% of eamino caproic acid, and from 75% to 90% of hexamethylene diammonium adipate, all percentages expressed being by weight, the said filament characterized by a shrinkage tension to shrinkage ratio of less than 0.7, a boil-off shrinkage of 8-15%, an initial modulus no greater than 12 grams/denier and a tenacity of at least 4 grams/denier, wherein the shrinkage tension is determined by immersing a given length of yarn into water at a temperature of 90 C.i1 C. for about five minutes, restraining the yarn to prevent shrinkage, Withdrawing the sample and allowing it to dry at room temperature for about five minutes, and measuring the yarn tension in grams/ denier, said initial modulus and said tenacity being determined after relaxed state boil-off of said filament.

10. The filament of claim 9 further characterized by an nuclear magnetic resonance loosening factor of at least 1.2.

11. A composition of matter consisting essentially of the terpolymer of from 2% to 20% hexamethylene diammonium sebacate, from 5% to 13% of e-amino caproic acid and from 75% to 90% of hexamethylene di-arnmonium adipate, all percentages expressed being by Weight,

wherein an oriented filament consisting essentially of said 1 composition is characterized by an nuclear magnetic resonance loosening factor greater than 1 and a boil-01f shrinkage of from 8%-15%.

10 References Cited UNITED STATES PATENTS FOREIGN PATENTS 1/1946 Great Britain.

OTHER REFERENCES A.P.C. Application of Moller et al., Ser. No. 364,354,

published 4-43, abandoned. 5

WILLIAM H. SHORT, Primary Examiner. H. D. ANDERSON, Assistalnt Examiner. 

1. AN ORIENTED FILAMNENT CONSISTING ESSENTIALLY OF AN INTERPOLYMER COMPOSITION SELECTED FROM THE GROUP CONSISTING OF: (1) THE COPOLYMER OF FROM 10% TO 20% OF E-AMINO CAPROIC ACID AND FROM 80% TO 90% OF HEXAMETHYLENE DIAMMONIUM DIPATE, AND (2) THE TERPOLYMER OF FROM 5% TO 20% OF E-AMINO CAPROIC ACID, UP TO 20% OF HEXAMETHYLENE DIAMMONIUM SEBACATE AND FROM 75% TO 90% OF HEXAMETHYLENE DIAMMONIUM ADIPATE, ALL PERCENTAGES EXPRESSED BEING BY WEIGHT, THE SAID FILAMENT BEING CHARACTERIZED BY A SHRINKAGE TENSION TO SHRINKAGE RATIO OF LESS THAN 0.7 AND A BOIL-OFF SHRINKAGE OF 8-15%, WHEREIN THE SHRINKAGE TENSION IS DETERMINED BY IMMERSING A GIVEN LENGTH OF YARN INTO WATER AT A TEMPERATURE OF 90*C.$1*C. FOR ABOUT FIVE MINUTES RESTRAINING THE YARN TO PREVENT SHRINKAGE, WITHDRAWDRAWING THE SAMPLE AND ALLOWING IT TO DRY AT ROOM TEMPERATURE FOR ABOUT FIVE MINUTES, AND MEASURING THE YARN TENSION IN GRAMS/DENIER. 